Analysis of a novel thyroid-specific DNA binding activity in the Pax8 promoter

Thyroid organogenesis requires the coexpression of the four transcription factors Pax8, Hhex, Foxe1 and Ttf-1 which mark a restricted number of cells in the ventral wall of the primitive pharynx as precursors of thyroid follicular cells. These factors act in a combinatorial way for which each controls the expression of the other but none of these alone induces the specification of thyroid precursors; to date there are no data available on the specification process. The study of cis-regulatory elements of thyroid specific selector genes would be the first step in the elucidation of the transactivating factors estabilishing the thyroid-specific molecular network. In particular we have been focused on the regulation of the pax8 gene that is the first of the four above mentioned selector genes to be expressed and we've found a novel thyroid-specific DNA binding activity on its promoter. The analysis of this DNA-activity could provide insights into the thyroid specification process.